Hey baller, it really depends on what you're preferences are. Do you want strong contrast fades (honeycombs, whiskers, stacks, etc.) then you could wait... up to 12 months. But if you want them to show a little more subtle, you could wear them around 5/6/7 months and then wash.
Best thing you can do is just don't give a shit and wash when they stink, because they WILLLL become awesome. Don't think about it too much unless you have strong preferences.